The Apple Watch spO2 sensor and outliers in healthy users

Abstract

It is unclear how frequently the Apple Watch produces spO2 measurements outside of the normal range in healthy individuals at rest. We conducted a head-to-head comparison in 38 healthy individuals between two watches and two medical-grade pulse oximeters. Fourteen percent of watch measurements yielded spO2 values below 95%, with no values below 92%. Results suggest that outliers measured by the watch should not be a cause for concern in otherwise healthy individuals.